After having given this a bit of additional thought (and undertaken a little bit of minor digging into MLS) I do think there are some things America needs to address and which if they get correct will greatly enhance their prospects
Coming to this relatively fresh they have a great chance to survey some of the structural issues that afflict other nations, notably England and the other 'emerging' new power (Africa as a collective entity)
In England the aspirations of the national team are very much a secondary consideration and suboridinated to an all powerful club structure. The demands of the national team(s) are very much seen as a distraction by club managers that they frankly wish would go away and quietly combust. This is largely our own fault. We have created a Frankenstein monster called the Premiership and with the money that's sloshing round, we've also learned this last month (though had suspected it for ages) that there are number of English internationals who don't want to play for England because they're frightened of being subjected to a critical scrutiny and derided by fan and media alike, which they're less likely to encounter amongst tribal morons blindly following their clubs. In any event, the clubs pay the salaries, and that's the most important thing in their eyes
The lessons I would draw from that is the following
America needs to balance the demands of developing a stronger domestic proving ground, with the need to keep the national team on the apex of the focus. In England they're divorced. It's often difficult to keep these in equilibrium and somewhere along the line a natural order evolves, or a conscious decision is taken to give one primacy. In cricket and rugby for instance the national teams are seen as the flag carriers and actually perform a much stronger economic role in generating money that trickles down. Both of Englands rugby and cricket teams have won a world cup or been ranked number 1 during the last 15 years. Our football team has never got close.
If American players are sent into Europe, and most worryingly of all, England, they'll fall under this regime. Don't do it. Send them to the technical leagues of Holland, France, Spain or Germany (keep them away from Italy too). The African nations are beset with governance issues on top of other things, but many of their better players have fallen under the Premiership curse and trying to keep a team toegther with a globally dispora of personnel is a nightmare to manage
Ideally try and send players on scholarship leases that enable you to manage their workloads and availability. In cricket we call it central contracting, and its possible here because the money is earned on the international apex. In other words, they're contracted and paid by the national board. The English FA couldn't do this for footballers because it simply hasn't got the money to compete with the Premiership clubs. If the American footballing authorities can do though, they'd be better advised to centrally contract players and lease them to European teams I reckon.
Doing this would have an additional benefit I believe for a country that can only play one major tournament every 4 years (something that I think will change soon). The MLS season isn't particularly long, nor is it particularly sensibly structured. It needs to be more competitive, and there are clearly some fault lines, but also some quite neat contrived areas of competition enhancement too i quite like such as 'rivalry shields' or whatever they're called. What the current schedule permits though is extended downtime that could be really productively used for national training camps.
The concept of a training camp is much more engrained in the American sporting landscape than it is Europe's. I suspect your players will respond this much more positively than ours who often give the impression of thinking they're above this kind of thing. Looking at the current calender you could get 3 months of training camp into a year (England's would be lucky if they got 10 full days coaching time with the national team in a year). If you centrally contracted, and if a major broadcaster signed up the national team as a partner, you could make the MLS more competitive by playing fewer matches on a promotion and releagtion basis, and then spend the rest of the year developing as a national team, whilst playing high profile friendlies or contrived TV tournaments, cherry picking your opposition
It's no wonder Jurgen is smiling, he can see what he's potentially sitting on